Fix for SCons 1.2.0: problem with detection of g77 on MinGW.
Still need to test on Linux.
Modified ascend-config for Windows to output paths with double backslash, seems to fix a problem with ParseConfig in SCons 1.2.0.

Added '--models' option to ascend-config.
Fixed a bug with packages.c wrt generating absolute paths to library files.
Added SCons directives to install header files in INSTALL_INCLUDE subdirs.
Changed rel.c so that init function is only run if provided in the package.
Added 'ospath_getabs' to convert relative paths into absolute paths by adding prefix of fully-resolved '.'

Fixed up behaviour of default ASCENDLIBRARY in python interface (for the case
where you're using ascpy without using the PyGTK GUI).
Removed some debug output when loading external libraries.
Fixed up the 'extfntest' example & SConscript file.